Cant answer as such, just to say it happend to me after I was given a thieves guild quest to steal from the stables in one of the large towns (Forget which one). Looks like the same place as your screenie ! The only difference is ... One of my duplicates is stuck in the ground, up to his waist :)
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TerryApr 14 '12 at 19:11

Louis Letrush should no longer duplicate at the Whiterun Stables fast-travel marker or attack the player for no apparent reason.

If it doesn't fix it or you'd rather not install it, you could also 'remove' Louis Letrush from the game, but it's better to do this after you've already finished the quest related to Louis Letrush (Promises to Keep), to avoid bugs related to that quest.

Make a save game first, and then in the game, open up the console by pressing ~, then click on one of Letrush's clones (RefIDs of the clones start with 'FF', original does not start with 'FF'), type disable and then markfordelete. This will 'remove' the Louis clones from the game. I'd do this for each clone, and then try to keep the original Louis. You may disable and markfordelete the original Louis if you want to, too.

From this source, it says: "Upon entering the city at whiterun stables, after completing the quest 'Promises To Keep', upto 3 or 4 Louis Letrush's can spawn there" As far as I no there is no solution but I dont think this is too major of a bug so you should be fine

I play on PS-3. I started with two standing and one half buried in the road after finishing the quest. It jumped to four standing and one half buried soon after.
A dragon attacked outside Whiterun and two guards were killed. Now I have seven all standing around, walking into each other. No other game problems encountered though it does make for an amusing scene whenever I return to Whiterun to see these guys all fidgeting around in a cluster.

I had this problem too, on the PS3. I think I got up to 7-10 Louis's total.
However, when I downloaded Hearthfire and Dawnguard, the next time I went to the stables, there were ZERO Louis Letrush's. I don't know if it was the DLC that fixes it or a patch I don't know about, but the problem's fixed.